STALLING

2003 GMC Savana

2003 GMC Savana, 90000 mi.
More and more often, whenever I come to a stop or slow down for a turn, the engine will either stall or stutter. When it's idling it also sputters and sometimes stalls out. It's worse with the AC on.
I've had plugs, wires, coils, checked out and short of pulling ever injector out and cleaning for 200 a piece, I'm lost. Help please.